Stoking installation for feeding solid fuel to a furnace



1956 M. VAN UYE PIETERSE 3,

STOKING INSTALLATION FOR FEEDING SOLID FUEL TO A FURNACE 3 Sheets-Sheet 1 Filed Aug. 22, 1963 F/GJ.

INVENTOR M and: 1 4 lye Pi 1966 M. VAN UYE PIETERSE 3,223,515

STOKING INSTALLATION FOR FEEDING SOLID FUEL TO A FURNACE 5 Sheets$heet 2 Filed Aug. 22, 1963 INVENTOR [Ar/a! 1m L7: P/H'wua.

puma ll fi k/- ATTORNEY 1966 M. VAN UYE PIETERSE 3,228,515

STOKING INSTALLATION FOR FEEDING SOLID FUEL TO A FURNACE 3 Sheets-Sheet 5 Filed Aug. 22, 1963 6 w Ff INVENTOR ATTORNEY United States Patent 3,228,515 ST OKING INSTALLATION FOR FEEDING SOLID FUEL TO A FURNACE Marius van Uye Pieterse, The Hague, Netherlands, as-

signor to N.V. Stookwerk, Rijwijk, Netherlands Filed Aug. 22, 1963, Ser. No. 303,779 12 flaims. (Cl. 198104) This invention relates to a stoking installation for feeding solid fuel to a furnace, especially a boiler furnace with the furnace either in front of the boiler or within the boiler as with underfeed stoking. More specifically the stoking installation is of the kind including upper and lower rotary screw conveyors, the lower one extending from the fuel hopper and the upper one extending to the furnace, and includes means for propelling the fuel between the two adjacent ends of the conveyor.

A stoking installation of the aforesaid kind has already been propose-d in British patent specification No. 698,822 in the name of A. C. van Rijswijk, but the installation of said specification has the following disadvantages namely:

(21) Since the fuel is propelled between the conveyors by a third screw conveyor the height between the discharge opening of the fuel hopper and the inlet opening of the furnace is necessarily limited.

If, on the other hand more than three screw conveyors are provided, for propelling in more than the three stages, illustrated and described in British patent specification No. 698,822, the whole installation would become more costly.

(b) In effect, in said previously proposed installation there are used three separate coal bunkers, i.e., three consecutive large-bore cylindrical parts in each of which is mounted a helical fuel-propelling screw.

An object of the present invention is to obviate or mitigate the above disadvantages irrespective of the height between the furnace inlet and the fuel hopper outlet.

According to the present invention we provide a stoking installation for feeding solid fuel to a furnace of the kind referred to, wherein the fuel propelling means comprises an elevator having a series of fuel engaging scoops movable in an endless path to raise the fuel from the lower screw conveyor to the upper screw conveyor.

However in practice it has become apparent that in the feeding of lumpy combustibles such for example as wet coals, these coals are propelled, more or less in lump form, from the lower screw conveyor towards the elevator, but they never reach the coal-engaging scoops of the elevator, remaining instead at the front-face of the chain wheel.

In other words, the coals neither slide nor roll away on issuing from said screw conveyor, but instead they jam up together against the chain wheel, until finally the screw conveyor ceases to operate owing to the jamming effect of the compressed mass of the combustible material.

The object of the present invention is to obviate or mitigate the above disadvantage. According to the present invention in a stoking installation for feeding fuel to a furnace, rotary fuel-propelling means are mounted between the bottom cowl of the elevator casing and the outlet of the lower screw conveyor to ensure a continuous flow of fuel into the cowl for engagement by the scoops of the elevator.

Preferably the scoops are mounted between a pair of parallel endless chains or bands engaging top and bottom pairs of wheels carried by extensions of the screw conveyor shafts, the chain wheel adjacent to the upper screw conveyor being centrally apertured to admit the extension of the screw, shaft and conduit of said upper screw conveyor.

Preferably also, the elevator is enclosed by a casing or housing of which the top and bottom ends are formed as cowls permitting passage of the elevator scoops, and from which scoops the fuel is discharged in the upper cowl into the inlet of the upper screw conveyor. The extensions of the screw, shaft and conduit of said upper screw conveyor lie in the space between the two parallel endless chains or bands.

T 0 ensure efficient freeing or loosening of the fuel from the elevator into the inlet of the upper screw conveyor, the screw has, according to another important feature, at this point a larger diameter and a greater speed than the remaining portion of the screw extending into the furnace of the boiler.

A further characteristic of this invention is that the extension of the conduit of the upper screw conveyor at the fuel inlet point is provided with a substantially semicylindrical lower portion having at each top side upwardly inclined parts directed respectively to the right and to the left for efficient guiding of the fuel from the scoops into the conduit of the upper screw conveyor.

Preferably the rotary fuel-propelling means are in the form of a multi-bladed propeller rotatable in a large-bore cylindrical casing or drum.

According to one construction, the propeller has six blades so that for each revolution as it were six pieces of the fuel are pushed to the elevator.

A further feature of the invention is that the plurality of blades of the propeller are mounted in an oblique direction on a hub more especially by welding, whereby the hub is formed as an upright annular plate mounted to a bearing sleeve secured to the conveyor shaft.

Further according to the invention the elevator casing adjacent to the cylindrical drum is extended and carries a bearing sleeve for the shaft of the lower screw conveyor.

Two embodiments of the invention will now be described by way of example with reference to the accompanying drawings, in which:

FIG. 1 shows the installation applied to a boiler with the furnace in front.

FIG. 2 shows the installation applied to a boiler with the furnace in the boiler (either with underfeed stoking or with another fuel feeding arrangement).

FIG. 3 is a fragmentary longitudinal section of the installation showing details of the elevator and screw conveyors.

FIG. 4 is a transverse section on the line A-B of FIG. 3.

FIG. 5 is a fragmentary longitudinal section through another embodiment of the invention showing the elevator, screw conveyors and bladed propeller.

FIG. 6 is a transverse section on the line C-D of FIG. 5.

FIG. 7 is a transverse section the line E-F of FIG. 5.

Referring to the drawings:

A stoking installation for feeding solid fuel to a furnace 1 consists of a lower rotary screw conveyor 2 extending horizontally from the bottom of a fuel hopper 3, an upper rotary screw conveyor 4 extending horizontally to the furnace 1. This furnace may be located either in front of the boiler (FIG. 1) or within the boiler 5 as with underfeed stoking (FIG. 2). The ends of said screw conveyors 2, 4 remote from the hopper 3 and boiler 5 are located vertically one above the other, and a substantially-upright elevator 6 extends between said vertically adjacent ends.

The elevator 6 consists of a series of fuel-engaging scoops 7 mounted between a pair of parallel endless chains 8, 9 engaging top and bottom pairs of chain Wheels 10, 11, 12, 13 connected respectively to extensions of the shafts 14, 15 of the upper and lower screw conveyors 2, 4, so that the axes of the screw conveyors coincide with the centers of the chain wheels 10, 11, 12, 13. The vertical planes in which the ascending and descending stretches 3 of the elevator 6 move are normal to the axes of both conveyor shafts 14, 15.

The elevator 6 is enclosed by a casing or housing 16 of which the top and bottom ends form cowls 17, 18.

The bottom cowl 17 serves as a tray for the fuel, and the upper cowl 18 permits passage of the elevator scoops 7. The tray 17 communicates with the outlet of the lower screw conveyor 2 which thus charges the scoops 7, whereas said scoops are discharged in the upper cowl 18 into the inlet of the upper screw conveyor 4.

An extension of the upper screw conveyor 4 projects into the cowl 18 and lies in the space between the two chains 8, 9 of the elevator 6 to receive the fuel discharged from the scoops 7. The upper pair of chain wheels 12, 13 are interconnected by a peripheral series of axial rods 19, and the chain wheel 13 adjacent to the upper screw conveyor 4 is centrally apertured (aperture 20), the extension of the shaft 15, screw 21 and conduit 22 of the upper screw conveyor 4 passing through aperture 20.

In order to ensure efficient freeing or loosening, of the fuel from the elevator 6 into the inlet of the upper screw conveyor 4, the screw 21 has at this point a larger diameter 23 and a greater speed than the remaining portion of the screw 21 extending into the furnace 1 of the boiler 5. For efiicient guiding of the fuel from the scoops 7 into the conduit 22 of the upper screw con- 'veyor 4, the extension of said conduit 22 at the fuel inlet point is provided with a substantially scmicylindrical lower portion 24 having at each top side upwardly inclined parts 25, 26, directly respectively to the right and to the left.

Preferably the conduits 22, 27 of the screw conveyors 2, 4 and the casing or housing 16 of the elevator are connected to each other by welding or the like.

The top of the fuel hopper 3 is in the form of an apertured platform 28 on to which a tipping lorry 29 is driven to discharge the fuel into the hopper 3.

Driving means 30 connected to an end of the lower conveyor-shaft 14 projecting from the elevator casing 16 operates the screw conveyors 2, 4 and the elevator 6. It will be clear that said driving means 30 can alternatively be connected to the shaft 15 of the upper screw conveyor 4.

It will be understood that the invention is not restricted to the details of the embodiment above described which may be varied without daparting from the broad ideas underlying it.

So it is possible to use instead of two endless chains or hands, between which the scoops are mounted, one single chain or band.

Also one can instead of using an underfeed stoker, as illustrated in FIG. 2 provide a stoker in accordance with that described and claimed in my US. patent application Serial No. 209,113 with the furnace also within the boiler as by an underfeed stoker.

The second embodiment is a stoking installation with improved means as above explained, whereby between the bottom tray or co wl 17 of the leasing or housing 16, by which the elevator 6 is enclosed and the outlet of the lower screw conveyor 2 there is provided a large bore cylindrical drum 31. Rotatably mounted in drum 31 is a fuel-propellor consisting of plurality of blades 32 mounted in an oblique direction on a hub.

Said blades 32 are welded to the hub, which is an annular plate 33 welded to a bearing sleeve 34 secured to the lower conveyor shaft 14 e.g. by means of a key.

The elevator casing 16 adjacent to the cylindrical drum 31 is extended at 35, and carries a hearing sleeve 36 for the shaft 14.

It will be clear that the locals in lump form regularly move into the path of the propellor blades 32, and the lumps are thus divided into smaller particles which slide away or are pushed piece by piece under the chain wheel to the elevator scoops 7.

According to the construction as illustrated the propellor has six blades 32 so that for each revolution in fact six pieces are pushed towards the elevator 6.

It will be understood that the invention is not restricted to the details of the embodiment above described, which may be varied without departing from the broad idea underlying it.

Thus, it is possible instead of a bladed propellor to provide a feed screw of the same diameter as said propellor.

Also it is possible instead of the scoops being mounted between a pair of parallel endless chains, to secure same to a single chain or band.

What I claim is:

1. A stoking installation for feeding solid fuel from a fuel hopper to a furnace, comprising a furnace; upper and lower rotary screw conveyors having parallel axes, said lower screw conveyor extending from the fuel hopper and having a discharge end located at a level below said upper conveyor and said upper conveyor extending to said furance, and means for propelling the fuel between said discharge end and said upper conveyor, said fuel propelling means comprises an elevator having a series of fuel-engaging sco'ops movable in an endless path to raise said fuel from said lower screw conveyor to the upper screw conveyor, said fuel engaging scoops being movable from said lower to said upper conveyor in a substantially vertical plane which is normal to the axes of said screw conveyors.

2. A stoking installation according to claim 1 further comprising a cylindrical drum having a large bore, and a rotatable fuel-propellor, mounted in said bore, said drum being located between the bottom portion of said elevator and the discharge end of said lower screw conveyor to ensure a continuous flow of fuel into said bottom portion for engagement by said scoops of the elevator.

3. A stoking installation according to claim 1 wherein said elevator further comprising a pair or" parallel endless flexible members, and a pair of upper and a pair of lower wheels respectively carried by extensions of the screw conveyor shafts each of said flexible members trained around and engaging one upper and one lower 'wheel, the wheel adjacent to the upper screw conveyor being centrally apertured to admit the extension of the screw shaft and conduit of said upper screw conveyor.

4. A stoking installation according to claim 1 further comprising a housing enclosing said elevator the top and bottom ends of said housing being formed as cowls permitting passage of the elevator scoops, and from which scoops are discharged in the upper cowl into the inlet of the upper screw conveyor the fuel from the scoops, whereby the extensions of the screw, shaft and conduit of said upper screw conveyor lie in the space between the two parallel endless chains or bands.

5. A stoking installation according to claim 1 wherein to ensure efi'icient freeing of the fuel from the elevator into the inlet of the upper screw conveyor, the screw has a larger diameter adjacent said elevator and a greater speed than the remaining portion of the screw extending into the furnace of the boiler.

6. A stoking installation according to claim 1 wherein the extension of the conduit of the upper screw conveyor at the fuel inlet point is provided with a substantially semi-cylindrical lower portion having at each topside upwardly inclined parts directed respectively to the right and to the left for efficient guiding of the fuel from the scoops into the conduit of said upper screw conveyor.

7. A stoking installation according to claim 2 wherein the fuel propellor in the large bore cylindrical drum is in the form of a multibladed member having preferably six blades fixedly mounted in a oblique direction on a hub.

8. A stoking installation according to claim 2, wherein the hub comprises an upright annular plate mounted to a bearing sleeve secured to the conveyor shaft.

9. A stoking installation according to claim 4, wherein that portion of the elevator housing which is adjacent to the cylindrical drum is extended and carries a bearing sleeve for the shaft of the lower screw conveyor.

10. A stoking installation for feeding solid fuel from a fuel hopper to a furnace, comprising an upper and a lower rotary screw conveyer, said lower screw conveyer extending from the fuel hopper and having a discharge end spaced from the hopper, and said upper rotary screw conveyer extending to the furnace and having an inlet end spaced from the furnace and located at a level above said discharge end of said lower conveyer; and means for raising the fuel from said discharge end of said lower conveyer to said inlet end of said upper conveyer, said means comprising a pair of spaced lower rotary wheels coaxial with said lower screw conveyer, a pair of spaced upper rotary wheels coaxial with and coupled to said upper screw conveyer for rotation therewith, one of said pair of upper rotary wheels being provided with a central opening through which a portion of said upper conveyer extends, said inlet end of said upper conveyer being located in the space between said pair of upper wheels, a pair of spaced parallel endless flexible members respectively trained around and operatively engaging corresponding ones of said pairs of wheels, means for driving said members along an endless path, and a series of fuel engaging scoops located between and connected to said members and movable in said path for raising fuel from the discharge end of said lower conveyer to the inlet end of said upper conveyer when said members are being driven, said scoops being arranged to discharge into the space between said pair of upper rotary wheels and onto said inlet end of said upper conveyer.

11. A stoking installation as set forth in claim 10, further comprising a housing between said upper and lower screw conveyers and housing said endless flexible members, said upper and lower wheels, and said scoops, said housing including a large bore cylindrical drum extending therefrom coaxially with said lower screw conveyer, and a rotatable fuel propeller located in said drum intermediate said housing and said discharge end of said lower conveyer and coaxial therewith so as to insure a continuous feeding of fuel into the lower portion of said housing for engagement with said scoops, said rotatable fuel propeller being provided with a plurality of blades mounted in oblique manner on said lower screw conveyer shaft, said propeller having an effective diameter larger than the diameter of said lower screw conveyer.

12. A stoking installation for feeding solid fuel from a fuel hopper to a furnace, comprising an upper and a lower rotary screw conveyer, said lower screw conveyer extending from the fuel hopper and having a discharge end spaced from the hopper, and said upper rotary screw conveyer extending to the furnace and having an inlet end spaced from the furnace and located at a level above said discharge end of said lower conveyer; and intermediate conveyer means for raising fuel from said discharge end of said lower conveyer to said inlet end of said upper conveyer, said intermediate conveyer means comprising an upper and a lower rotary member respectively coaxial with the corresponding screw conveyer, drive means for driving at least one of said rotary members, an endless flexible member trained around and operatively engaging said rotary members, and a plurality of fuel transporting scoops connected to said flexible member for movement along an endless path when said drive means are actuated, said path including an arcuate portion at said upper rotary member and said inlet end of said coaxial upper rotary screw conveyer extending within said arcuate portion of said endless path of said fuel transporting scoops, whereby fuel transported by said scoops from said discharge end of said lower conveyer is discharged into said inlet end of said upper screw conveyer when the respective scoop is in said arcuate portion of its path.

References Cited by the Examiner UNITED STATES PATENTS 2/1925 Lauterbur 198-404 6/1954 Best 198l04 

1. A STROKING INSTALLATION FOR FEEDING SOLID FUEL FROM A FUEL HOPPER TO A FURNACE, COMPRISING A FURNACE; UPPER AND LOWER ROTARY SCREW CONVEYORS HAVING PARALLEL AXES, SAID LOWER SCREW CONVEYOR EXTENDING FROM THE FUEL HOPPER AND HAVING A DISCHARGE END LOCATED AT A LEVEL BELOW SAID UPPER CONVEYOR AND SAID UPPER CONVEYOR EXTENDING TO SAID FURNACE, AND MEANS FOR PROPELLING THE FUEL BETWEEN SAID DISCHARGE END AND SAID UPPER CONVEYOR, SAID FUEL PROPELLING MEANS COMPRISES AN ELEVATOR HAVING A SERIES OF FUEL-ENGAGING SCOOPS MOVABLE IN AN ENDLESS PATH TO RAISE SAID FUEL FROM SAID LOWER SCREW CONVEYOR TO THE UPPER SCREW CONVEYOR, SAID FUEL ENGAGING SCOOPS BEING MOVABLE FROM SAID LOWER TO SAID UPPER CONVEYOR IN A SUBSTANTIALLY VERTICAL PLANE WHICH IS NORMAL TO THE AXES OF SAID SCREW CONVEYORS. 